Wrong line for adding syntax hightlighting in the emacs init file

[Pierre Vial]

On the tutorial page of the project: [https://deducteam.github.io/tutorial.html], it is indicated to add the following line to the .emacs init file:
(add-to-list package-archives '("melpa" . "http://melpa.milkbox.net/packages/"))

An apostrophe is missing just before package-archives (should be 'package-archives instead).
Moreover, the line
(add-to-list 'package-archives '("melpa-stable" . "https://stable.melpa.org/packages/"))
seems to work fine